1. Field of the Invention
The present invention relates to an ion source generating ions by plasmatizing a gas, an ion implanting device using such an ion source, and a manufacturing method of semiconductor devices using such an ion implanting device, and particularly, to the ion source, the ion implanting device, and the manufacturing method of semiconductor devices suitable for use in manufacturing micro-structured semiconductor devices.
2. Description of the Related Art
In recent years, high integration of semiconductor devices used in electronic equipment, communication equipment, and so on advances more and more and integrated elements are becoming more micro-structured. It can be said that LSIs (large scale integration) thus integrated have a great influence on performance of the entire equipment in which they are used.
The shrink of the integrated elements is realizable by shortening the gate length and thinning source/drain regions, for example, in the case of a MOS (metal oxide semiconductor) field-effect transistor. A low-acceleration ion implanting method is widely used for forming shallow source/drain regions. To implant ions in a semiconductor substrate using this method makes it possible to form the shallow source-drain regions of 100 nm or shallower at present.
Incidentally, an ion implanting device to carry out the low-acceleration ion implanting method requires at least an ion source and an ion introducing/guiding system which extends from this ion source to a substrate to be processed (semiconductor substrate). As for this ion source out of these constituents, a device, which plasmatizes a predetermined gas by arc discharge to generate ions, is generally used. Devices for plasmatizing the gas are roughly classified into a Bernus type and a Freeman type which use a thermal electrode and a microwave type which uses a magnetron. Incidentally, a device described, for example, in Japanese Patent Laid-open Application No. 2001-93431 is one of the conventional ion generating devices.
In the ion implanting device, the ion source is usually replaced at the maintenance time. This is because, when the ion implanting device is operated for use in manufacturing a semiconductor device and so on, the ion source is gradually deteriorated so that a desired operation is not performed. In an ion implanting device including, for example, a Bernus-type ion source and forming source/drain regions having a depth of approximately 70 nm, the replacement cycle of the ion source is, for example, 170H (hours) on average.
Further, in order to use such an ion implanting device for forming source/drain regions having a depth of, for example, approximately 20 nm, a method of, for example, giving a low energy of 5 kev or lower at the highest to generated ions for acceleration is usable. The formation of the source/drain regions having a depth of approximately 20 nm is indispensable for manufacturing a further micro-structured MOS transistor (in terms of the gate length, corresponding to a MOS transistor having a gate length of 100 nm or less).
It has been confirmed, however, that the life of the ion source is remarkably shortened when the ion implanting device is applied to such a low acceleration. An average value of the life in this case is, for example, 60 H to 70 H. It can be supposed that the life is thus shortened due to the fact that the use for the low acceleration lowers the efficiency of outwardly drawing out the generated ions so that the amount of the generated ions needs to be increased to such an extent sufficient to compensate for this efficiency degradation. The generated ions work as a factor of deteriorating the ion source as described later.
When the life of the ion source is thus shortened, it greatly influences productivity and production cost in manufacturing semiconductor devices. The estimation of the degree of the influence shows that approximately 50 more replacement parts of the ion source are necessary in a year compared with the case where the source/drain regions having a depth of approximately 70 nm are formed, and the working time increases by about 200 H provided that the working time of 4 hours is required for one maintenance. Accordingly, a yearly expenditure of, for example, more than 11 million yen per one ion implanting device is newly necessary for the cost of the replacement parts and manpower.